Corrige ReferenceError: handleConfirmUnsubscribe is not defined

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/Library.tsx

@@ -63,6 +63,12 @@ export default function Library() {
     },
   });
 
+  const handleConfirmUnsubscribe = () => {
+    if (confirmDeleteId) {
+      unsubscribeMutation.mutate(confirmDeleteId);
+    }
+  };
+
   const handleLogout = async () => {
     try {
       await authService.logout();